A. 1-2-3-4 B. 1-3-2-4 C. 2-1-3-4 D. 2-3-1-4 参考答案:A
第8题:[单选题]pH和体积相同的HAc溶液和HC1溶液,分别与过量Na2CO3溶液反应,在相同条件下,放出的CO2的体积是( )。 A.一样多 B.HCl比HAc多 C.HAc比HCl多 D.无法比较 参考答案:C H A C是弱电解质,部分电离。在体积相同的溶液中,要和H Cl溶液的pH相同,则必须H A C的原始浓度》H Cl的浓度。在与N A2 CO3发生反应时,由于平衡 移动,可使原来未电离的H A C不断电离而与N A2 CO3作用。当N A2 CO3为过量时,与H A C 作用放出 CO2更多。
第11题: [单项选择]What do we learn about deserts from this text A. Deserts can change into green and fertile areas. B. Certain areas have always been desert. C. Deserts were once the home of elephants and giraffes. D. Deserts have been growing since the beginning of the worl 参考答案:A 答案解析:文章第二段第六行“Throughout history deserts have been expanding and retreating again.”这段中谈到,一些肥沃的地方以前曾经是沙漠,而